1. Field of the Invention
The present invention relates to insulating multiple glazing units with at least one gap filled with gas, particularly air, especially the windows of transportation vehicles, and more particularly the windows of aircraft.
2. Discussion of the Background
The fuselage of an aircraft constitutes a metal envelope that ensures an electromagnetic shielding function. Similarly, the windshield of an aircraft is metallized, for example by incorporation of a conductive and transparent layer used for deicing. In this way the aircraft instruments susceptible to disturbance by an electromagnetic field are insulated.
Nevertheless, the electromagnetic shielding of the fuselage contains xe2x80x9celectromagnetic holesxe2x80x9d in the form of the windows. In fact, the windows, which are generally formed from double glazing units of poly(methyl methacrylate) with an interposed air gap, do not ensure the function of electromagnetic shielding.
With the advent of mobile phones and portable computers that the passengers use during their aircraft trips, the need for ensuring continuity of the electromagnetic shielding of the aircraft has now arisen. These portable devices can actually cause disturbances, which interfere with communications between the flight crew and the control tower. For safety reasons, therefore, it is now becoming imperative to insulate the interior of aircraft completely by providing continuous electromagnetic shielding.
The present invention brings a solution to this problem. To this end, it is provided according to the present invention that at least one electrically conductive thin layer is incorporated in the actual glazed section of the windows and that the peripheral window seals are made conductive.
The first object of the present invention is therefore an insulating multiple glazing unit whose glazed section is provided with at least two superposed panes of mechanically strong transparent substrate, between which there is interposed at least one gap filled with gas, generally air, the said panes being mounted at their periphery in a seal, by means of which the said glazing unit can be built into a structure designed to enclose a space containing instruments susceptible to being disturbed by an electromagnetic field and which has an electromagnetic shielding function, characterized by the fact that the glazed section is provided with at least one continuous electrically conductive transparent thin layer, and in that the seal is made conductive at least in part in order to ensure connection of the said electrically conductive transparent thin layer or layers to the said structure, the conductivities of the said electrically conductive transparent thin layer or layers and of the said seal being chosen to ensure continuity of the electromagnetic shielding of the said structure.
In general, the panes of mechanically strong, transparent substrate are made of one-piece glass plates (soda lime glass) or of polymer plates, such as poly(methyl methacrylate) (PMMA) or of laminated glass plates of the type of those in which a sheet of polyvinylbutyral (PVB) or of polyurethane (PU) having a thickness of generally between 0.3 and 2 mm is sandwiched between two sheets of PMMA. Traditionally, these plates can be plane or curved or arched. The glazing units that are particularly preferred, because they are the most common, are the double glazing units.
Preferably, it is provided that the transparent electrically conductive thin layers applied according to the present invention are disposed in the interior of a multiple glazing unit, such that these layers are protected from mechanical impacts and scratching. Nevertheless, the electrically conductive layer can even be deposited on an exterior face of the glazing unit, particularly on the interior side of the aircraft, where xe2x80x9coverglazingxe2x80x9d, also known as xe2x80x9cdecorative window treatmentxe2x80x9d, is generally present and even permits a certain degree of protection of the layer.
According to a first embodiment of the present invention, at least one electrically conductive transparent thin layer is constituted by a layer of doped semiconductor or metal oxide, deposited by cathodic sputtering under vacuum, especially by magnetron, or by liquid-phase or gas-phase pyrolysis if the substrate is resistant to heat (inorganic glass) or by any other deposition technique (immersion, spraying, sol-gel, etc.), having a thickness of between 100 nm and 1000 nm and a surface resistivity of 2 to 40 xcexa9/xe2x96xa1, particularly 15 to 30 xcexa9/xe2x96xa1, a layer of doped semiconductor oxide being:
(a) either disposed to cover at least one face of a pane which is a component of this glazing unit, preferably a face turned toward the interior of the multiple glazing unit;
(b) or included in the body of a substrate pane;
(c) or even deposited on at least one face of a transparent thin film of poly(ethylene terephthalate) (PET) type, or of a thin glass plate, the said film or the said plate constituting an additional layer in the glazed section.
The doped semiconductor oxide constituting these transparent electrically conductive thin layers is in particular indium oxide doped with tin (ITO) or tin oxide doped with antimony or fluorine. ITO is particularly preferred.
As indicated hereinabove in point (a), the transparent electrically conductive thin layers are preferably deposited on substrate panes which are turned toward the interior of the insulating multiple glazing unit. Thus the double glazing units in which at least one internal face is covered by a layer of doped semiconductor oxide can be mentioned as particularly preferred.
To achieve version (b), according to which an electrically conductive thin layer is included in the body of a substrate pane, such a thin layer can be deposited on at least one face of a transparent PET film (F), and this film (F) can be used to form a laminated glass of PMMA/PVB or PU/(F)/PVB or PU/PMMA type.
In the case of version (c), it can be provided that the thin filmxe2x80x94or the thin glass platexe2x80x94is coated on one of its faces by the layer of semiconductor oxide and is applied, for example by adhesive, on one face of a pane which is a component of the multiple glazing unit. It can also be provided that such a filmxe2x80x94or such a platexe2x80x94coated on at least one of its faces, is clamped parallel to the panes, in an intermediate space filled with gas, means being provided to hold the filmxe2x80x94or the platexe2x80x94at its periphery in the seal; the seal can therefore be provided with an additional retaining groove for the film or the plate. The clamped film can also be applied against a pane and introduced together therewith into the corresponding groove of the seal.
The thin film of PET type that can be used in versions (b) or (c) has in particular a thickness on the order of 25 to 150 microns, especially from 50 to 125 microns. As regards the thin glass plate that can be used in version (c), it can have a thickness on the order of 0.5 to 2 mm, especially 0.5 mm to 1 mm.
According to a second embodiment of the present invention, at least one electrically conductive transparent thin layer is constituted by at least one metal layer M inserted between two layers of a dielectric transparent material D of high optical index, in such a way as to form a stack of DMD type or a stack formed by a combination of several base stacks, such as DMDMD, the stack being disposed so as to cover one face, preferably a face of a pane which is a component of the glazing unit, the face being turned toward the interior of the glazing unit.
In particular, the metal layer M is a layer of gold or silver, and the dielectric transparent material D of high optical index is tin dioxide or zinc sulfide.
The different layers constituting these stacks are deposited in well known manner by evaporation or by cathodic sputtering under vacuum. They each have a thickness on the order of 50 to 500 nanometers (10xe2x88x929 m).
In general, the double glazing units in which at least one of the faces, preferably an internal face, is coated by a DMD or DMDMD stack such as just defined can be mentioned as particularly preferred.
As already indicated, the layers can be on an external face of the glazing unit and in particular on the interior face in the aircraft, especially when a xe2x80x9cdecorative window treatmentxe2x80x9d is present.
Also, when one of the panes constituting the multiple glazing unit of the window is a laminate, the layers can be disposed in the body of the pane, applied on one of the internal faces of one of the constituents of the laminate: on one of the sheets of glass and/or even on a film, especially PET, integrated into the laminate.
According to the present invention, the seal in which the actual glazed section of the insulating multiple glazing unit is mounted is made from an elastomer which advantageously comprises a silicone or fluorosilicone that has been made conductive at least in part by incorporation into its composition of an electrically conductive filler formed from metal granules or fibers, especially of silver, copper, aluminum, nickel, silver/copper, silver/aluminum, silver/glass, etc., or from carbon black, the conductive elastomer having in particular a volume resistivity of 2xc3x9710xe2x88x925 to 2xc3x9710xe2x88x923 ohmxc2x7m (0.002 to 0.1 ohmxc2x7cm), the electrically conductive thin layer or layers being in contact with a conductive part of the seal, which is also designed to make contact with the structure to be provided with electromagnetic shielding.
It is self-evident that the base elastomer from which the seal is made has all the properties required for the application under consideration: Shore hardness A, tearing strength, permanent compressive deformation, elongation at break, etc., and that the incorporation of the conductive filler has not substantially modified these properties. In particular, the Shore hardness A of the seal is advantageously from 30 to 80.
According to a particularly advantageous first modified embodiment, the seal is produced from elastomer made conductive throughout its composition.
According to another version, the seal is made by comolding of two elastomers, one of which is the conductive elastomer of the invention and is disposed so as to cooperate with the electrically conductive thin layer or layers of the invention. It will be advantageously provided that the conductive part of the seal is the internal part, which can be more easily made to cooperate with the overall structure to be provided with electromagnetic shielding.
Moreover, if the conduction of the seal proves to be insufficient, it is possible according to the present invention to provide for endowing the seal with a conductivity boost, comprising in particular:
a conductive film, for example of tinned Cu, or a metal mesh or a conductive paint, for example an Ag lacquer, applied on at least one part of the seal surface; and/or
a metal hoop or metal foil or metal mesh or adhesive metal tape placed at the periphery of the glazing unit or at points or regions of the periphery, against at least one internal part of the seal, in such a way as to make contact with an electromagnetic thin layer and/or with the structure to be provided with electromagnetic shielding; and/or
a conductive enamel or a conductive paste deposited on a conductive thin layer and making contact with the seal or, as the case may be, with a metal hoop or foil or tape at the periphery of the glazing unit or at points or regions of the periphery.
In a particularly preferred embodiment, the insulating multiple glazing unit of the present invention comprises an aircraft window provided with electromagnetic shielding with a rating of at least 10 db, particularly 10 db to 30 db.